1. Field of the Invention
The present invention relates to a tilt and lift device used for adjusting height and tilt angle of a Venetian blind, more particularly one, which can be smoothly operated even if the original tilt cord and lift cord thereof are replaced with thicker tilt cord and lift cord suitable for use with Venetian blinds with large and heavy slats.
2. Brief Description of the Prior Art
Referring to FIGS. 1 and 2, a conventional tilt and lift device of a Venetian blind includes a manual control member (not shown), a supporting base 10, a support 20, a reel tube 30, an external tube 40, and a transmission shaft (D).
The manual control member is secured on an uppermost part of a door (window), and connected to the transmission shaft (D) such that the transmission shaft (D) can be turned in a selected direction by means of operating the manual control member. The supporting base 10 is securely held in a horizontal elongate part (C) on an upper part of the door (window), and it has a holding space 101, a through hole 102, and a locating portion 103 next to the through hole 102. The support 20 is secured to the locating portion 103 of the supporting base 10, and it has a passage 201, and internal threads. The reel tube 30 has a continuous spiral groove 301 on an outer side, and a hole 302 near to a first end. A lift cord is passed through the hole 302, and formed with a knot at an inner end, and wound along the continuous spiral groove 301 of the reel tube 30. The reel tube 30 is positioned horizontal in the holding space 101 of the supporting base 10, and passed through the passage 201 of the support 20 while the lift cord is passed through the through hole 102 at the other end, passed through the slats of the Venetian blind, and joined to a lowermost one of the slats. The external tube 40 has an annular groove 401 on one end, and it is positioned horizontal in the holding space 101 of the supporting base 10 with the reel tube 30 being passed into it. A tilt cord is passed over the external tube 40, and held in the annular groove 401 at a middle portion, and joined to front edges of the slats at a front portion, and joined to rear edges of the slats at a rear portion. The transmission shaft (D) is passed through and joined to both the external tube 40 and the reel tube 30 such that the tubes 30 and 40 will turn together with the transmission shaft (D). Because of friction between the external tube 40 and the tilt cord, which is passed over the external tube 40, and held in the annular groove 401, the tilt cord will be slightly moved when the external tube 40 is turned.
Thus, height and tilt angle of the Venetian blind can be changed by means of operating the manual control member to turn the transmission shaft (D). Because of the external threads of the reel tube 30 and the internal threads of the support 20, the reel tube 30 will move linearly relative to the support 20 when it is turned. If the user wants to adjust both the height and the tilt angle of the Venetian blind, he should adjust the height of the Venetian blind first; after the Venetian blind has been adjusted to a desired height, the user should operate the manual control member to make the external tube 40 slightly turn in a direction opposite to the last one such that the slats of the Venetian blind are adjusted to a desired tilt angle.
The above conventional tilt and lift device has the following disadvantages:
The device can only be used with a certain thickness of lift cord and tilt cord, as shown in FIG. 3; if the original lift cord is replaced with one with excessive thickness, the new one will be jammed between the external tube and the reel tube, as shown in FIG. 4, and the Venetian blind can't be smoothly moved; if the original tilt cord is replaced with a thicker one or a thinner one, there won't be enough friction between the new tilt cord and the external tube, as shown in FIG. 4, and the tilt angle of the slats can't be effectively adjusted. Consequently, the tilt and lift device can only be used with Venetian blinds lighter than a certain weight, and it can't be used with large and heavy Venetian blinds because the original lift cord and the original tilt cord thereof aren't strong enough.
Referring to FIG. 5, another tilt and lift device of a Venetian blind includes a manual control member (E), two tilt tubes 91, two reel tubes 92, and a transmission shaft. The transmission shaft is connected to the manual control member (E), the tilt tubes 91, and the reel tubes 92 such that the tilt tubes 91, and the reel tubes 92 will be turned when the manual control member (E) is operated. The reel tubes 92 are arranged outsides the tilt tubes 91; thus, when a thick lift cord is used in the place of the original one, it won't be jammed between the tilt tubes 91 and the reel tubes 92 to hinder rotation of the reel tube. And, lift cords are connected to the reel tubes 92 and the slats of a Venetian blind, and tilt cords are connected to the tilt tubes 91 and the slats. And, the tilt tubes 91 are made in such a way as to allow thick tilts cord to be used thereon instead of the original ones. Therefore, the second conventional tilt and lift device can be equipped with thick lift cords and tilt cords, and used with large and heavy Venetian blinds.
However, the second conventional device has a more complicated structure and higher manufacturing cost than the first one, and it takes more time and labor to assemble the second device. Therefore, the second conventional tilt and lift device isn't economical to use.